A round baler is used in agriculture to collect or gather crop lying or standing on a field and to press and bind it into a bale. The baler is towed behind a tractor and comprises a frame on which a baling chamber, radially surrounded by bale forming means, is provided. The bale forming means consist of driven rafters, belts or chains with slats or a combination of two or more of those. Crop is collected from the ground fed into the baling chamber and baled there. Finally, a bale is wrapped with a twine or net or film and deposited on the ground when it has reached a desired size, density or mass.
The power for driving the bale forming means is, in the prior art, generally provided by the engine of the tractor that pulls the baler over the field. The engine drives a power take off (PTO) that drives a transmission of the baler via a universal joint shaft. The baler transmission on its end drives the rollers of the baling means or rollers driving the belts or chains of the baling means via associated drive trains.
It has been also proposed to drive a number of auxiliary components of a baler with electric motors, for example an arm of a binding mechanism (DE 28 01 309 A1) or a wrapping material dispenser (DE 41 32 664 A1). The energy source for the electric motors is provided on board the tractor. It has also been proposed to mount an electric generator on board the baler in order to drive an electric motor for the binding mechanism (EP 1 273 217 A1).
A self propelled rectangular baler with an electrically driven plunger is described in WO 94/24845 A2. Further, DE 10 2007 015 649 A1 describes a rectangular baler driven during a start-up phase with an electric motor, and DE 196 21 391 A1 and DE 196 28 604 A1 describe rectangular balers with a split drive having a first branch mechanically driven from the tractor and a second, electrically driven branch in order to maintain a desired drive speed.
Finally, EP 1 174 019 A1 describes a self propelled harvesting machine in the form of a combine or forage harvester. Crop feeding conveyors and processing elements like threshing drums or cutter heads are driven by electric motors that are mounted inside the rotationally driven element.
A disadvantage of the typical mechanical drive of the bale forming means is seen in the complexity, need for regular service, for example lubrication, and in the fixed rotation speed and direction. The electric motors driving auxiliary components of the balers do not drive the bale forming means, but only elements that just need a limited amount of power. Electric drives providing more power are only known in the context of rectangular balers and self propelled harvesting machines, but not for round balers.
Thus, it is an object of the invention to provide a round baler in which one or more of the aforementioned problems are overcome.